Horizontal Resisted Motion Questions (1 Viewer)

[zacn]

I can't seem to calculate these questions, help would be appreciated.

1. A 14kg object is rolling along a horizontal path at 21 m/s. If frictional forces amount to 1.2 times its speed, what will its speed be after 11s?

2. A bicycle is free-wheeling along a horizontal path at 33 m/s. If its deceleration is 0.02 times the square of its speed, what will its speed be after 4s?

Thanks

 

[idkkdi]

I can't seem to calculate these questions, help would be appreciated.

1. A 14kg object is rolling along a horizontal path at 21 m/s. If frictional forces amount to 1.2 times its speed, what will its speed be after 11s?

2. A bicycle is free-wheeling along a horizontal path at 33 m/s. If its deceleration is 0.02 times the square of its speed, what will its speed be after 4s?

Thanks

Horrible questions, it doesn't make physical sense to say frictional forces amount to 1.2 times its speed. I will assume it means the value x 1.2.

1. 21 x 1.2 = F
F/14 = a

v = u + at (plug and chug)

2. 33^2 x 0.02 = a
v = u + at (plug and chug)

Edit: just noticed it was ext 2 maths. If this is not posted in the wrong subject, then my solution is probably wrong.

 

[zacn]

This is ext 2

 

[idkkdi]

This is ext 2

You sure that these questions are worded like this? Are they from a reputable source? and does 1.2 x etc. mean x the magnitude?

 

[tito981]

The frictional force is a function of its speed so I dont think you can use the kinematic equations.

 

[Canteen]

I think this is what it means.
1.






2. Is similar method with a different function.

Sorry for bad layout; can't seem to get the align function to work!